Yes, that's Bill Gates on stage with him at the very end.
So I checked out Khan Academy, and I have to say I am very impressed. Khan's "lectures" -- I hesitate to call them lectures, though, because they're quite informal, conversational, and Khan doesn't bother to polish them up, which is probably helpful for students who feel intimidated by the material -- are engaging and hit just the right note. They don't feel dumbed-down, nor do they make unwarranted assumptions about what the student knows. Whether he's teaching advanced calculus or how to add and subtract fractions, Khan aims his lectures perfectly at the student's likely level of knowledge.
Although the lectures go all the way up to very advanced mathematics and also cover areas such as physics and finance, Khan Academy's practice modules are limited to pure mathematics. They start (literally!) with 2 + 2 = 4 and continue up through high school math. Not much calculus and other advanced math, but the site is continually creating new modules, and I think new ones may have appeared just in the past two weeks. Problems are randomly generated, and once you solve ten consecutive problems correctly, you are declared proficient in that module. Make one mistake, and you have to get another ten in a row right.
Practice modules are arranged on a knowledge map which reminds me of upgrade trees from turn-based strategy computer games. The student gets awarded various badges, for such distinctions as solving ten consecutive problems within a short span of time, or earning proficiency in a certain number of modules.
This brings me to what impresses me most about Khan Academy. Make no mistake, the site is intended primarily for schoolchildren. The video game mechanics I alluded to in the previous paragraph will appeal to kids. Khan wasn't invited to speak at TED for helping adults re-learn arithmetic they'd forgotten years earlier. But there's nothing cute or childish about the presentation. As the site's blog says, "Kids are smarter than we give them credit for." An adult can start the modules with the most basic addition exercises without feeling strange or self-conscious.
I'm working my way up through the practice modules. Right now I'm at 34 completed out of 107, but that makes my progress sound more impressive than it is. Basic arithmetic modules are behind me, while precalculus is still ahead of me.
I find that working through these modules without using a calculator brings an unexpected side benefit: I can practice focus. Like many people in this day and age, my attention span feels damaged due to easy Internet connections and mobile devices. When I let my mind wander while I'm working my way through a Khan Academy module, I make careless mistakes. If I make even one careless mistake, my streak gets reset and I have to start all over, correctly answering ten more problems in a row before I'm declared proficient in a module.
I've also downloaded Khan's finance lectures to my iPod Touch -- with all of the Taiwanese finance experts I train in English in my job, I feel I'd better have a more thorough knowledge of the field.